Feature request: Show timestamps on chat messages

Description

Add timestamp display next to each message in the chat UI (both user messages and Claude's responses).

Use case

When reviewing conversation history, it's helpful to know the exact time each message was sent/received. Currently there's no visual timestamp — users can't tell when a conversation happened without checking history.jsonl manually.

Suggested format

Show time (HH:MM) next to each message, e.g.:

• [11:00] User: Hello
• [11:01] Claude: Hi there

Notes

• history.jsonl already stores timestamps per message, so the data exists — just needs UI rendering
• Could be an optional setting for users who want it